Certain features of said previous application shown and described, but not claimed therein, are shown and described and claimed in the present application, and other features of the previous application shown, described and claimed therein are shown and described, but not claimed, in the present application. Other features are shown, described and claimed for the first time herein.
1. Field of the Invention
The present invention pertains to the efficient utilization of fuel. Even more specifically, the invention relates to the efficient utilization of fuel such as oil fuel or gas fuel burning in a furnace, usually a domestic furnace, although not necessarily so. The present invention differs from that of the initially filed application which related to the burning of fuel, including coal, wherein the flue gas stream included particulate material. Pursuant to the present invention, there is little or no particulate material in the flue gas, and the particulate material that is present principally takes the form of soot. Even this only is present when oil is burning and is almost entirely absent when gas is burning. A gas flame is very clean and creates essentially no particulate loading. An oil flame may, and frequently does, have some toxic material in its products of combustion and, as a rule, a gas flame has no toxic fumes in its products of combustion. The combusted gas stream issuing from a furnace that is burning gas does not require cleaning, and the combusted gas stream that is fed to a smokestack from a burner that is operating with a properly balanced oil burner does not, as a rule, require very much cleaning. The special field of the instant invention is particularly concerned with the recovery of heat from the stack gas of domestic furnaces and, in the process, reducing the temperature of the stack gas to, or close to, ambient temperature.
More particularly, the present invention pertains to a heat recovery system in which stack gases from an oil- or gas-fired domestic furnace are diverted in their passage to a chimney and routed through a heat recovery unit where the heat from the waste gases is recovered and used, for example, to heat tap water which subsequently can be employed for domestic hot water or as a hot air preheater. The present invention has several other features too numerous to describe at this point but which will be pointed out as the description proceeds.
2. Description of the Prior Art
The recovery of low level, previously wasted heat from sources such as flue gas has received attention in recent years because of the energy crisis. The cost of conventional fuels such as oil, coal, and especially natural gas, has escalated to the point where it is now profitable to install ancillary heat recovery units to recover previously wasted heat contained in system effluents such as flue gas. The problem of efficiently and usably recovering such heat is compounded by the fact that it is available only at a relatively low temperature level and, in the case of flue gas, the sensible and latent heat contained in the gas must be recovered from a large quantity of gas having a low heat content. Flue gas produced by burning sulfur-containing fuels is of an extremely corrosive nature, especially when the flue gas is scrubbed by aqueous media which generates sulfurous and sulfuric acids in situ.
Heat recovery schemes of various types are shown in U.S. Pat. Nos. 1,986,529; 2,878,099; 3,169,575; 3,439,724; 1,083,885 and 4,129,179.